Loads (such as lighting devices and air conditioners) in a station building normally operate with power supplied from commercial power supply. However, because it is conceivable that power supply from the commercial power supply is stopped in a case of a power stoppage and the like, the station building power supply device includes a power supply circuit that enables to maintain power supply to the loads in the station building even in a case of emergency such as a power stoppage of the commercial power supply. This power supply circuit includes a main circuit and a control circuit for controlling semiconductors constituting the main circuit. The main circuit receives power supply from an overhead wire carrying a direct current of, for example, 1,500 volts, or 750 volts, converts the power into an alternating current, and then supplies the alternating current to the loads in the station building. The control circuit executes ON and OFF control of the semiconductors of an inverter constituting the main circuit and stops the system upon detecting an abnormality based on the voltage, current, frequency, and the like of the main circuit, for example. Patent Literature 1 discloses an electric-railway power supply apparatus that causes a power regenerative inverter in a power substation to operate as a self-commutated inverter, to thereby supply emergency power when the power supply from commercial power supply to the loads in a station building is stopped.